I will add my 2 cents on the matter.
I have successfully connected this kind of an SD slot board to the DUET 2 "CONN_SD" port
The board has both 3.3V and 5V input, I went with 3.3V. Connecting it is really rather easy, get the DUET pinout diagram and make connections from DUET "CONN_SD" to the board, GND to GND, CS to CS, MISO to MISO and so on.
I used an ethernet solid core cable and in total its maybe around 1m long. So far I have two over 8h long prints behind me and so far with no issues.